Origin of the term
The term "gun slinger" was used in the Western film Drag Harlan (1920). The word was soon adopted by other Western writers, such as Zane Grey, and became common usage. In his introduction to The Shootist (1976), author Glendon Swarthout says "gunslinger" and "gunfighter" are modern terms, and the more authentic terms for the period would have been "gunman", "pistoleer", "shootist," or "bad man" (sometimes written as "badman"). Swarthout seems to have been correct about "gunslinger", but the term "gunfighter" existed in several newspapers in the 1870s, and as such the term existed in the 19th century. Bat Masterson used the term "gunfighter" in the newspaper articles which he wrote about the lawmen and outlaws whom he had known. However, Joseph Rosa noted that, even though Masterson used the term "gunfighter", he "preferred the term 'mankiller'" when discussing these individuals. Clay Allison (1841–1887), a notorious New Mexico and Texas gunman and cattleman, originated the term "shootist".
Often, the term has been applied to men who would hire out for contract killings or at a ranch embroiled in a range war where they would earn "fighting wages". Others, like Billy the Kid, were notorious bandits, and still others were lawmen like Pat Garrett and Wyatt Earp. A gunfighter could be an outlaw—a robber or murderer who took advantage of the wilderness of the frontier to hide from genteel society and to make periodic raids on it. The gunfighter could also be an agent of the state, archetypically a lone avenger, but more often a sheriff, whose duty was to face the outlaw and bring him to justice or to personally administer it. There were also a few historical cowboys who were actual gunfighters, such as the outlaw cowboy gang who participated in the bloody Skeleton Canyon Massacre.